The wavelength of the UV light being applied to the photoresist coating during the photolithography step of the semiconductor manufacturing process limits the ability to decrease the geometric size of the IC components. Indeed, the optical contrast, which determines the size of the IC component, is directly proportional to the wavelength of the UV light being projected onto the photoresist coating.
Conventionally, photolithography has used UV lights generated from lights containing krypton fluoride (KrF) and argon fluoride (ArF). These chemicals produce UV lights with wavelengths ranging from 193 nm to 248 nm. In such conventional KrF/ArF photolithography processes, the photoresist coating comprises an acid deprotectable or crosslinkable polymer, a photoacid generator (PAG), and a base quencher. In a KrF/ArF photolithography process, when the KrF/ArF UV light strikes the surface of the photoresist coating, the PAG absorbs the electromagnetic waves of the UV light and generates acid. Thereafter, the acid reacts with the photoresist polymer; changing chemical property of the photoresist polymer to make it soluble for the ensuing developing step. However, as the sizes of IC components became smaller, the ArF/KrF lithography processes became obsolete due to the relative long wavelengths of the ArF/KrF UV lights.
Accordingly, a photolithography method that uses UV lights with much shorter wavelengths was developed. Specifically, the EUV lithography uses UV lights that contain electromagnetic waves with wavelengths of about 13.5 nm. However, PAGs cannot absorb such low-wavelength UV lights. One aspect of the EUV photolithography processes is the inclusion of a photosensitizer to the photoresist coating. When the EUV light strikes the photoresist coating, the photosensitizer absorbs the short-wavelength electromagnetic waves and releases photoelectrons. These photoelectrons then react with PAGs to generate acid. Thereafter, the acid reacts with the photoresist polymers changing the chemical properties of the photoresist polymers, much like the conventional KrF/ArF photolithography process.
However, while the EUV photolithography uses short-wavelength UV lights to create smaller IC components, it has some drawbacks. First, the EUV photolithography is inefficient—the photosensitizers and PAGs in the photoresist coating typically convert only 5 percent of the short-wavelength electromagnetic waves into acid. Moreover, the photoelectrons generated within the photoresist coating dissipate energy as heat. This excess amount of heat may cause photoresist outgassing.
Accordingly, what is needed is a method and photoresist material for manufacturing an integrated circuit device that addresses the above stated issues.